/*
   =============================================================================
	readrn.c -- read a random sector from a file
	Version 8 -- 1987-12-15 -- D.N. Lynx Crowe

	int
	ReadRN(fcp, buf)
	struct fcb *fcp;
	char *buf;

		Reads a sector from file 'fcp' into 'buf'.  Seeks as needed.
		Returns 0 if OK, -1 for errors, 1 for EOF (no data returned).
   =============================================================================
*/

#define	DEBUGIT		0

#include "stddefs.h"
#include "biosdefs.h"
#include "errno.h"
#include "errdefs.h"
#include "fspars.h"

#if	DEBUGIT
extern	short	fsdebug;
#endif

#if	TBUFFER
extern	long	_secrd();
#endif

extern	long	_berrno;
extern	int	_seek();

/* 
*/

/*
   =============================================================================
	ReadRN(fcp, buf) -- Reads a sector from file 'fcp' into 'buf'.
	Seeks as needed.  Returns SUCCESS (0) if OK,  FAILURE (-1) for errors.
   =============================================================================
*/

int
ReadRN(fcp, buf)
struct fcb *fcp;
char *buf;
{
	int	sv;		/* seek return code */
	long	brc;		/* bios return code */

	if (sv = _seek(fcp))		/* try to find the sector we want */
		if (sv < 0) {

			errno = EIO;		/* I/O error */
			return(-1);		/* return:  ERROR */

		} else {

			errno = EINVAL;		/* invalid argument */
			return(1);		/* return:  EOF */
		}

#if	DEBUGIT
	if (fsdebug)
		printf("ReadRN():  curlsn=%ld, curdsn=%ld, offset=%u\n",
			fcp->curlsn, fcp->curdsn, fcp->offset);
#endif

#if	TBUFFER
	if (brc = _secrd(buf, (short)fcp->curdsn)) {
#else
	if (brc = BIOS(B_RDWR, 0, buf, 1, (short)fcp->curdsn, 0)) {
#endif

		_berrno = brc;			/* log the error */
		errno = EIO;			/* ... as an I/O error */
		return(FAILURE);		/* return:  ERROR */
	}

	return(SUCCESS);		/* return:  SUCCESS */
}